Cement-kiln plant and method of operating- the same



I. E. BELL.

CEMENT KTLN PLANT AND METHOD oF oPERATlNG THE sANE.

APPLICATION FILED AUG.2, 191B.

Z l li Patented 0011. 18, 1921.

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Patented Oct. 18', 1921.

l. E. BELL.

CEMENT KTLN PLANT AND NETHon 0F OPERATING THE SAME.

Y APPLICATION FILED AUG.2T 1918. 1,393,788.

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CEMENT KILN PLANT ANDMETHOD 0F OPERATING THE SAME.

I. E. BELL.

APPLICATION FlLED/AUG.2,I9I8.

Patented Oct. 18, 1921.

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sem/257K Flag'- ooooono oooooooo 2q VEA/TOR l. E. BELL.

CEMENT KILN PLANT AND METHOD 0F OPERATING THE SAME. APPLICATION FILEDAuf-L2, 1918.

FIG- 7 Luid Arron/vm1 UNITED STATES PATENT OFFFI@ JOI-IN E. BELL, OFBROOKLYN, NEW YORK.

CEMENT-KILN PLANT AND METHOD 0F OPERATING THE SAME.

To all whom t may concern.'

`true and eXact description, reference being had tothe accompanyingdrawings, which form a part thereof, n

My present invention comprises improvements in the construction,arrangement and method of operating cementkiln systems in which the hoty gases leaving the cement kilns are passedk through so-called wasteheat boiler furnaces in which the heat contained in the gases ispartially absorbed and utilized. My invention relates particularly to asystem in which a plurality of rotary cement kilns are used. The generalobject of the invention is to provide a plant construction andarrangement and method of operating same which will be simple andreliable, and will give a desirably high efficiency without entailingprohibitive costs of installation, operation and maintenance.

The heating of steam generating boilers by the hotgases leavingindustrial furnaces of many kinds, including rotary cement kilns, hasbeen often proposed, and has been practised with success in someinstances, but the effective utilization of the heat contained in thehot gases issuing from rotary cement kilns presents specialdiliiculties, and so far as I am aware no satisfactory plan of utilizingthe gaseous products from a vbattery of rotary cement kilns in heatingsteam generating boilers has been developed prior to my presentinvention.

rllhe special difficulties standing in the way of the effectiveutilization of the hot gases from rotary cement kilns in waste heatboiler furnaces include or arise from various factors or circumstances.There are usually several rotary cement kilns in each battery or unit,the average number of kilns in each such unit in this country beingperhaps siX or seven. The volume of heated gas issuing from each kiln isrelatively large. The volume of gas and thefrequent necessity forcutting out portions of the plant for cleaning and repairs, as well ason account of irregularities in the output capacity required, make itdesirable to associate with lea/ch `ib a-tteiyof kilns :a plurality lofwaste Patented Oct. 1 8, 1921.

Application filed August 2, 1918. Serial No. 247,923.

heat boiler units. Practical operating considerations make it necessarythat the plurality of kilns for each unit or battery, and thecorresponding waste heat boilers, be connccted by a common fiue system,so that any one kiln or any one boiler furnace may be cutout of servicewithout necessarily interfering with the operation of the rest of thesystem. The hot gases leaving the cement kilns .carry with them arelatively large amount of flue dust, consisting mainly of particles ofthe finely ground stone from which the cement is made, and both theamount of this dust, and the difficulties to which it gives rise, areaugmented by the fact that the draft must be ample to give a highvelocity of gas flow past the heat absorbing surfaces of the waste heatboiler portion of the system, this high velocity being necessary toinsure a desirably high operating efficiency. The draft loss, or drop inpressure head, in the kilns proper is comparatively small and forms buta small fraction of the total draft or drop in pressure head necessaryto move the burning gases and products of combustion through the systemas a whole. This makes it difficult to obtain, and to preserve under thevarying conditions of operation, the necessary substantial uniformity ofdraft in the different kilns. The relatively large total draft requiredand the relatively high temperature, ordinarily about 1500o F., at whichthe hot gases leave the kilns, makes it both difficult and especiallyimportant to keep the air leakage into the flue system at a practicalminimum because of the injurious effectk on the plant efficiency of suchleakage. lllie leakage itself works against the efliciency in two ways;it increases the draft consumption and thereby increases the difficultyof maintaining the proper draft, and by lowering the temperature of theheated gases, it materially and directly reduces the efficiency of thewaste heat utilizing apparatus.

The specific object of the invention may be said to be such aconstruction and method of operating a cement kiln system comprising aplurality of kilns and a plurality of waste heat boiler furnaces, thatthe proper draft conditions may be maintained in the various kilns andin the various waste heat boiler furnaces by means of a commoncollecting and distributing flue system of such character as tofacilitate the temporary cutting .Out ofservice Voran individuel )Q19 9FFig. l. f

boiler furnace, and without an undesirably large loss of efficiency dueto heat radiation from the lue system or air leakage into the same, andwithout entaling a prohibitively high .cost of construction, maintenanceand operation.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a `better understanding of theinvention, however, and the advantages attending it reference should behad to the accompanying drawings and descriptive Vmatter in which I haveillustrated and described preferred constructions and methods ofoperation embodying my invention.

Of the drawings:

Figure l. is a somewhat diagrammatic plan with parts brokenv away and insection of a cement kiln system constructed in accordance with thepresent invention.

Fig. 2 is a partial section on the line 2-2 ot Fig. l.

Fig. 3 is a of Fig. 1.

Fig. t is a section on the line 4-4 ot partial section on the line 3 3Fig.` 5 is a view taken similarly to Fig. 1 illustrating a modifiedsystem.

Fig. 6 is a section on the line 6-6 oit Fig. 7 isa view taken generallysimilar to Fig. 1 illustrating a third construction'.

Fig. 8 is a partial section on the broken line 8 8 of Fig, 7.

lIn the system illustrated in Figs. 1 to a, inclusive, there are sevenrotary cement kilns A of ordinary construction, and each adapted todischarge the heated gases issuing from its upper end into a commoncollecting or bus channel E. which also serves to supply heating gasesthrough branches E to three separate steam generating boiler furnaces F.As shown, the upper or discharge end of each of the slightly inclinedkilns A opens directly' into an individual chamber or kiln head B. Eachkiln head B discharge either through a port C into the base of acorresponding individual stack C, or through a passageway D into thecommon orbus channel E. Provisions are made for ellecting a removableclosure ot each of the two outlets from the chamber B, since ordinarilyone ot these outlets must be closed when the other is open. Theremovable closure for the stack connection is formed, as shown, by meanso'l removable closure bars C2 disposed to cross a restricted portion C3fof the stack, preferably located immediately above the top ot' the portC. It is not necessary to describe 'this closure in detail since itsspecilic construction forms no part of the present invention andistfully disclosed, moreover, in my Patent-No. '1,311,435, `granted'July 29,

1919. The passage D, leading from each chamber B to the bus channel E isshown as generally horizontal, but is formed with its bottom wall in twoportions which are inclined downwardly away from the opposite sides of arestricted throat portion of the channel. A kerl D', formed in the wallof the channel D, at its throat portion, is normally illed by a U shapedbody J when flow through the passage D is permitted, and when flowthrough the passage D is cut oit, the kerf D is filled by the edge of aplate like damper or cut-off which then extends across the throatportion of the channel, as shown at JA in Fig. 6. The member J may beproportioned and arranged to partially obstruct and 'thus furtherrestrict the thro-.tt

portion Aof the corresponding passage D when this is desirable. Thejoints between the side walls of the kerl and the member. J or JA,filling the kerf are normally sealed by luting them with clay. Thisspecial construction of damper or cut-olf valve while novel with me isnot claimed herein.y but is disclosed and claimed in my Patent lllat.granted July 29,1919. The restriction of the passages D at their throatportions insures a high gas velocity through the throat portions,preventing liue dust from lodging in these restricted portions, and theinclination ot' the portions of the bottom wall of each passage D ateach side of the throat, minimizes the accumulation thereon of fluedust. The shape and capacity of the lower portions of the chambersaresuch as to permit considerable accumulations ot flue dust thereinwithout interference with the operation of the system, and theseaccumulations can be' removed from time to time through suitabh7disposed cleanout doors (not shown). The restriction of each passage Dat its throat exerts an important influence on the dra ft conditions,and the extent to which the throat is restricted depends upon the draftcontrolling effect desired as is hereinafter explained.

vThe bottom wall of the channel is inclined so that the flue dustdeposited thereon tends to go to one lower corner of the channel atwhich open distributed inlets I to dust removing'conveyer pipes Iruiming along the bottom of the channel. The passages E by which thechannel E is connected to the ditferent boiler furnaces proper are each'forme-:l

cleanout doors at the 'botbomfof'thefurnace l economizer.

Each boiler furnace is provided With an individual draft producing fanll, and interposed between each boiler furnace and the corresponding fanis an economizer or feed Water heater having its tubes transverse to thegeneral direction ot iloiv of the heating gases. G represents cleanoutdoors for the removal of flue dust Jfrom the bottom of the rllhe Wallsof the flue system connecting the difllerent kilns A, to the diiferentboiler furnaces F, must be lined with refractory material to withstandthe high temperatures of the gases passing through them, and areadvantageously formed with a relatively impervious and heat insulatingjacket around a fire brick lining in order to reduce heat radiation lossand leakage of air into the flue system.

lhe clinker forming material, or finely crushed cement forming stone, is'led into the upper ends or the various kilns A. by correspondingconveyer pipe portions l, arranged to pass one through each of thechambers B into the corresponding open kiln end. The tuel,V which may becoal, gas or oil for heating the kiln, and the air for supporting itscombustion, are 'ted into the ends ot the kilns remote from the chambersB, and regulated in the usual manner, which, as it is .vell known, neednot he illustrated or described herein.

ln the operation, the hot gases issuing out of the upper end of each oi"the kilns A pass into the correspondingchambers B at a temperature otabout 15000 F. From each chamber B the gases pass through the port C tothe corresponding stack C, when thc passage D" is closed, or in the morenormal condition When the stack C is sealed.` they pass through the thenopen passage D into the bus channel E. The gases flow through thechannel E to the outlets E through which that channel communicates withthe dii'lierent furnace chambers F. T he gases passing out olf thechannel E, through each passage lll', tlovv through the correspondingboiler' furnace F and economizer 'Gr to the corresponding fan H., whichdischarges the cooled gases either directlv into the atmosphere, or intosuitable discharge stack or conduit not Shown. ln any event the fansHrcreate the draft relied upon to carry the burning gases and productsof combustion through the kilns, the (lue system connecting the kilns tothe boilers, and through the latter and the econoniizers Gr. rlheeilective abstraction ci heat 'from the gases requires a comparativelyhigh velocity of iloiv of the gases over the heating tubes of the boilerand economizer. To obtain this the boiler and econornizer tubes shouldbe closely spaced. and the high velocity of ilovv., coupled with therestricted and tortuous character of the boiler and economiser llowpaths result in a substantial ,loss ot pressure head or draftconsumption in this portion of the apparatus. 'lhis high gas velocity isalso desirable to minimize the lodging of flue dust on boiler andeconomiser tubes. 'lhe bores ot the kilns A are straight and large indiameter and on this account offer little resistance to the flow ot theburning and healing through them. ln consequence the draft consumptionin thekilns is relatively small, and slight fluctuations in the pressureat the discharge end oiE a kiln produces a substantial and highlyundesirable variation in the amount and character oi the combustion inthe kiln. ln the cha-nnel l there is a. considerable longitudinal ilo'vvwhich varies different points owing to the distributed in-ilovv intothis channel from the different kilns, and this variable longitudinalflow creates diierences in static pressure ditlerent points along thelength of the latter., which react upon the dra-lt through the differentkilns and tend to make the dra'lit conditions in the diiiiercnt kilnsunequal. llfith the longitudinal llow in the channel E toward the endoi. the channel to which the furnaces F are connected the staticpressure at that end oi the channel must be loiver than it is at the endoi 'the channel remote from the furnaces. Furthermore. the eliect otfriction and the increase in velocity of ilovv as the furnaces areapproached. due to the distributive admission into the channel E alongits length from the various kilns il, both tend to increase thedifference between the static pressure at the end oit the channel E towhich thc furnaces F are connected and the opposite end oi the channel.The disturbing effect ci the change ot velocity and the friction loss lnthe channel E may advanta- ,tfeouslv compensated for to some extent hyma.V g the cross section of the channel increase the end ol the channelto Which the turn es F are connected in approached; and in ll l l havoshoivn the section ot the conduit into -which the 'four kilns nearestthe furnaces open larger in cross section than the section into whichthe other three kilns open. Practical pressure equilibrium cannot beobtained by this expedient.. houiever, even with all of the kilnscontinuously in regular operation. ll/lioreover. any such armroach toequilibrium as could be obtained under steady operating conditions, bvthus varying` the cross section ot the channel lt. would be destroyed.in practical operation, by disconnecting; any particular kiln A 'fromthe channel The variations in static pressure in the channel E could ybemade desirablv small. of course, by simply making the channel very largein. cross section. but this is not practically feasible because of theincrease in cost ot construction in heat radiation, and in liability tothe influir of air, resulting from a great increase in the size of thischannel, and in many cases space conditions would themselves make suchan enlargement in the cross section of the channel'E practicallyimpossible of attainment.

I have discovered, Yand the essence of my invention, in its broaderaspects, lies in this, that the disturbing effects in the kiln draft,due to variations in static pressure in a bus channel E of moderate andsuitable dimensions, may be reduced to an extent not seriouslyobjectionable by` the simple expedient of restricting `the passages Dconnecting the kilns tothe bus channel E, so that the drop in pressure,or draft consumed by the hot gases in flowing through these passagesbecomes substantially larger than the loss of pressure or draftconsumption in the individual kilns, and larger than the fluctuations inpressure in the bus channel E.

' F or example, with such an arrangement as is illustrated in Fig. l,the variation in static pressure between the points in the channel Eadjacent the endsx of the two kilns most remote from one another wouldbe in practice something like .2 of an inch of water. The draft orpressure loss in each kiln would be in the neighborhood of .2 or .3 ofan inch of water. Assume that the loss of head in the bus channel isonly .l of an inch of water and the effective kiln draft is .2 of aninch of water, then if the kilns were in unrestricted communication withthe channel E, and the pressure in the channel E. was such as to createthe proper draft of .2 of an inch through the kiln A, nearest thefurnace F, the draft through the kiln most remote from the furnaces Fwould be only Vbe more than 40% greater than the flow through the kilnmost remote from the furnaces. By restricting the connection between thekilns and the channel E so that the draft consumed by the passage of thenormal amount of gas through each of these restricted portions would besay of an inch, then the actual capacity of the two end flues would bein the rat-io of the square root of .4 to the square root of .5, and thecrpacity of the flue nearest the furnace would then be only about 12%greater than the capacity of the more remote flue. By increasing thepressure drop through the restricted connections between the kilns andfurnaces to an inch of water the change in capacity could be broughtdown to less than 5%. Practically a variation in draft of 5%, or even.10%, is not highly objectionable, as

such lagdraft variation can be compensated for, to a substantial degree,by adjustment of the air and fuel admission inlets to the remote ends ofthe kilns.

No provisions for varying or adjusting the restrictions or throttlingeffect afforded by the restricted portions of the various passages Dneed be provided. iu some cases, though where the passages D arethrottled more or less, under different operating conditions as by meansof dampers J partially obstructing the passages D, it is possible toobtain the desired draft equalization with a somewhat smaller totaldraft than is rcquired when the throttling effects, due to therestricted dimensions of the permanent walls of the throat portions ofthe passages D, are wholly relied upon. The effect of throttlin gcommunication between the various kiln heads and the common collectingflue E is, of course, to increase the total draft required. rl`heproduction of the extra amount of draft thus entailed is ordinarily nota serious matter. The extra draft does, of course, increase the tendencyto air leakage, but it is to be noted that this tendency to increasedleakage only exists with respect to the portions of the fiue and furnacesystem at the outlet sides of the kiln heads B, and does not exist inthe kiln heads proper, where, because of the necessity of providing forthe necessary motion of the kilns with respect to the kiln heads, it ismost difficult to guard against leakage.

viVhile changes in the static pressure in the portion of the conduit towhich the different boiler furnaces E are connected tend to disturb thedistribution through the boiler furnaces, the disturbance in this caseis much less serious than in the case of the kilns and can moreover beadequately compensated 'for by varying` the speed of operation` andhence the draft producing effects of the di fferent fans H when eachboiler furnace is provided with an individual fan. lVhcre thearrangement of the furnace system is such as to minimize the staticpressure variations at the inlets to adjacent waste heat boilerfurnaces, as is the case with the arrangement shown in Figs. 5 and G, itis not practically necessary to provide an indi` vidual fan for eachwaste heat unit, and in Fig. 5 one pair of adjacent waste heat units Fat the left of the figure are shown as provided with a common exhaustfan.

The desirabilitjv of regulating draft conditions by throttlingcommunication between the various kilns and the flue system into whichthey discharge is augmented by the fact that where the invention s usedin connection with waste heat recovery systems added to existinginstallations, as well as in wholly new installations, a great varietyof arrangements of kilns, boilers and connecting flues must be employed.Thus Figs. land 5 show plants differing materially from one another intheir general layout, while Figs. 7 and 8 show a third arrangementdiilering from 'the first two. ln Figs. 7 and 8 the collecting llue Eeirtends over the kilns A, and the connections D tothe kiln heads B,yare at the same side of the latter, as are the kilns A; thisarrangement being made necessary by the tact that space in `direction olthe length of the kilns is especially restricted. On account of thediversity in the plant layouts, which must be adopted in differentcases, it is especially dillicult to attempt to approximate staticpressure equalization in the collecting flue by tapering the latter,since the amount of taper which will give the best practical resultscannot be theoretically determined, but must be determinedexperimentally or be based upon past experience. lt will be understood,of course, that the three diiierent layouts illustrated, while typical,represent by no means the various iorms or kinds ot arrangement whichmust be employed in practice.

lllhile in accordance with the provisions oic the statutes l haveillustrated and described the best structural embodiments of myinvention, and the best modes of practising it now known to me, thoseskilled in the art will understand that changes may be made in the `lormof the apparatus, and method of operation disclosed, without departingl'rom the spirit of my invention as set forth in the appended claims."lhose skilled in the art will also understand that certain lea-tures ofmy invention may sometimes be used with advantage without acorresponding use of other features.

llaving now describedmy invention, what I claim as newand desire to.secure by lietters Patent, is: l

l; The method ot operating a cement kiln plant comprising a plurality ofrotary cement kilns, a waste heat boiler section and a flue into whichthe individual kilns open at points at varying distances from the boilersection, and which connects the series ol kilns to said boiler sectionwhich consists in throttling the connection between each kiln and theflue to such an extent as to make the pressure drop or draft consumptionbetween each kiln and the flue greater than the total pressure drop ordraft consumption in 'the tine and maintaining such draft conditionsthroughout the connected parts ol the system as will compensate for theresistance created by the throttling of saidv connections and bringabout a sutlicient and an approximately even draft in the kilns.

2. ln a cement kiln plant comprising` a series of rotary cement kilns, acollecting hue, one or more waste heat boiler sections connected to theflue and a series of connecting flues leading from the kilns to thecollecting due at points at varying distances from the boilerconnections, the construction ot the collecting Jlue and ol theconnecting lues from the kilns ci such normal tired proportions relativeto each other that the loss of pressure head in each said connectingflue is greater than the loss of pressure head in the collecting flueand the draft in the kilns thereby maintained atV such approximation touniformity as is necessary for their el'- ective working.

ln a cement kiln plant comprising a series of rotary7 cement kilns, acollecting flue, a plurality ol waste heat boiler sections connected tothe flue at dilterent points along its length and each provided with anindependent suction ifan to induce draft therein and a series ofconnecting lines leading from the kilns to the collecting ilue at pointsat varying distances trom the boiler connections, the construction otthe collecting tlue and ot the connectin lines from the kilns of suchnormal fixed proportions relative to each other that the loss otpressure head in each said connecting flue is greater than the loss olpressure head in the collecting flue and the dralt in the kilns therebymaintained at such approximation to unitormity is necessary lor theireffective working.

ln a cement kiln plant comprising a series et rotary cement kilns, acollecting line, one or more waste heat boiler sections connected to thellue, a series or" connecting Illues leading` from the kilns to thecollecting flue at points at varying distances from the boilerconnections and gates for closing each connecting flue at will, ktheconstruction of collecting liuc and ol the connecting lines :trom thekilns oit such normal fixed proi I'ons relative to each other that theloss or pressure head in each said connecting flue is greater than theloss of pressure head in the collecting line and the draft in the kilnsthereby maintained at such approximation to uniformity as is necessaryfor their effective working.

5. fi cement kiln` plant comprising a series or rotary cement kilns, aflue or chamber for each kiln into which it delivers its gas, a stackleading from each chamber, a common collecting line, one or more wasteheat boiler sections connected to the collecting ilue, connecting lluesleading from the stack chambers to the collecting flue and entering thesame varying distances from the points where the boiler sections connecttherewith, each ot said connecting tlues havsuch normal restricted andliz-,ted arcas as will about pressure drop therein in excess of thepressure drop in the collecting liu-e and thereby insure anapproximation to uniform drat't in the kilns, and valves whereby thegases from the kilns can be directed to the stacks or collecting finesat will.

6. A furnace system comprising a plurality of rotary cement kilns, astack and flue connection t0 said stack for each kiln, a col-y each kilnto they Collecting flue and valves for directing the gases from each-kilri to its stack or connecting flue at will, said connecting iluesleading ,to the collecting flue being structurally of such fixedrestricted area with reference to the urea of the kilns 10 having miinclined bottom and a dust collect- 15 ing chamber connecting therewith.

JOHN E. BELL.

